Contributions
Abstract: P441
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Intrathecal synthesis of immunoglobulin G (IgG) is a hallmark of multiple sclerosis (MS), with IgG1 being the dominant isotype. However, the mechanisms driving the IgG production remain enigmatic. We have recently shown that IgG1-secreting B cells of the G1m1 allotype are exclusively recruited to the cerebrospinal fluid (CSF) in G1m1/G1m3 heterozygous MS patients, whereas B cells of the G1m1 and G1m3 allotypes of IgG1 are evenly distributed in blood, as expected from random allelic exclusion.
Objectives: The selection of G1m1 positive B cells to the CSF could be driven by the target antigen of the B cells. To explore this possibility, we set out to determine the IgG1 allotypes of intrathecally synthesized antibodies against measles, rubella, and varicella zoster virus (VZV), which are believed to be the result of non-specific bystander activation of B cells in MS.
Methods: Paired CSF and serum samples from oligoclonal band (OCB) positive relapsing-remitting MS patients (n = 30) were screened for intrathecal IgG1 production against measles, rubella and VZV through isoelectric focusing and affinity blotting against nitrocellulose membranes coated with viral antigens. The G1m1 and G1m3 allotypes of the virus-specific antibodies were determined using affinity blotting and ELISA.
Results: We found intrathecal IgG1 synthesis against measles in 16/30 (53%), rubella in 16/30 (53%), and VZV in 15/30 (50%) patients. Collectively, we observed antibody production against either virus in 25/30 (83%) cases. The G1m1 skewing was maintained for all viral antigens, with 12/15 (80%; p = 0.013) cases of IgG1 against measles being exclusively of the G1m1 allotype, and similarly 14/16 (87.5%; p = 0.001) in the case of rubella and 14/14 (100%; p < 0.001) in the case of VZV. Similarly, ELISA results showed increased CSF/serum ratios for G1m1 as opposed to G1m3 directed against measles (2.05 vs. 1.46; p = 0.041), rubella (2.00 vs. 1.15; p < 0.001), and VZV (2.28 vs. 1.00; p < 0.001).
Conclusion: There is a strong G1m1 predominance of intrathecally synthesized antibodies against measles, rubella and VZV in G1m1/G1m3 heterozygous MS patients. This suggests that the selection of IgG1-secreting G1m1 B cells to the CSF of MS patients, and the perpetual intrathecal immunoglobulin synthesis, is driven by antigen-independent mechanisms.
Disclosure: Lossius A: reports grants from Sanofi Genzyme, during the conduct of the study; personal fees from Merck Serono, personal fees from Roche, outside the submitted work.
Holmøy T: has received speakers honoraria, and/or served on advisory board, and/or received unrestricted research grants from Biogen, Roche, Merck, Novartis, and Genzyme
Tomescu-Baciu A,Vartdal F, Vedeler CA: nothing to disclose.
Abstract: P441
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Intrathecal synthesis of immunoglobulin G (IgG) is a hallmark of multiple sclerosis (MS), with IgG1 being the dominant isotype. However, the mechanisms driving the IgG production remain enigmatic. We have recently shown that IgG1-secreting B cells of the G1m1 allotype are exclusively recruited to the cerebrospinal fluid (CSF) in G1m1/G1m3 heterozygous MS patients, whereas B cells of the G1m1 and G1m3 allotypes of IgG1 are evenly distributed in blood, as expected from random allelic exclusion.
Objectives: The selection of G1m1 positive B cells to the CSF could be driven by the target antigen of the B cells. To explore this possibility, we set out to determine the IgG1 allotypes of intrathecally synthesized antibodies against measles, rubella, and varicella zoster virus (VZV), which are believed to be the result of non-specific bystander activation of B cells in MS.
Methods: Paired CSF and serum samples from oligoclonal band (OCB) positive relapsing-remitting MS patients (n = 30) were screened for intrathecal IgG1 production against measles, rubella and VZV through isoelectric focusing and affinity blotting against nitrocellulose membranes coated with viral antigens. The G1m1 and G1m3 allotypes of the virus-specific antibodies were determined using affinity blotting and ELISA.
Results: We found intrathecal IgG1 synthesis against measles in 16/30 (53%), rubella in 16/30 (53%), and VZV in 15/30 (50%) patients. Collectively, we observed antibody production against either virus in 25/30 (83%) cases. The G1m1 skewing was maintained for all viral antigens, with 12/15 (80%; p = 0.013) cases of IgG1 against measles being exclusively of the G1m1 allotype, and similarly 14/16 (87.5%; p = 0.001) in the case of rubella and 14/14 (100%; p < 0.001) in the case of VZV. Similarly, ELISA results showed increased CSF/serum ratios for G1m1 as opposed to G1m3 directed against measles (2.05 vs. 1.46; p = 0.041), rubella (2.00 vs. 1.15; p < 0.001), and VZV (2.28 vs. 1.00; p < 0.001).
Conclusion: There is a strong G1m1 predominance of intrathecally synthesized antibodies against measles, rubella and VZV in G1m1/G1m3 heterozygous MS patients. This suggests that the selection of IgG1-secreting G1m1 B cells to the CSF of MS patients, and the perpetual intrathecal immunoglobulin synthesis, is driven by antigen-independent mechanisms.
Disclosure: Lossius A: reports grants from Sanofi Genzyme, during the conduct of the study; personal fees from Merck Serono, personal fees from Roche, outside the submitted work.
Holmøy T: has received speakers honoraria, and/or served on advisory board, and/or received unrestricted research grants from Biogen, Roche, Merck, Novartis, and Genzyme
Tomescu-Baciu A,Vartdal F, Vedeler CA: nothing to disclose.